to go somewhere secretly, or to take someone or something somewhere secretly

I managed to sneak in through the back door while she wasn't looking. 我趁她不注意从后门偷偷溜了进来。

Jan doesn't have a ticket but I thought we might sneak her in. 简没有票，但我想我们或许可以把她偷偷带进去。

I thought I'd sneak up on him (= move close to him without him seeing) and give him a surprise. 我打算趁他不注意悄悄走到他身边，吓他一跳。

to secretly tell someone in authority, especially a teacher, that someone else has done something bad, often in order to cause trouble

She was always sneaking on other kids in the class. 她总是向老师打小报告，说班里其他孩子的坏话。

to look at someone or something quickly and secretly

I noticed him sneak a look at what I was writing. 我注意到他悄悄地偷看了一眼我正在写的东西。

a person who tells people in authority when someone else does something bad

You told Mrs Cooper that it was me who tipped the paint over, didn't you - you nasty little sneak! 是你告诉了库珀夫人我打翻了油漆，对吗——你这卑鄙的告密者！

Synonyms: fink snitch